Hydroprocessing is important to the production of a wide range of chemicals and fuels. Hydroprocessing units can have many forms and purposes within a refinery and are often the most common processing and upgrading units. For example, hydrotreating capacity within a refinery can comprise over 55% of the total refining capacity. Hydroprocessing can also be one of the most energy intensive and costly processes of fuel and chemical processing facilities. One of the reasons for the high energy usage and cost, is the high hydrogen pressure, often greater than 68 psi, required by traditional techniques.
Generally hydroprocessing is the catalytic conversion and removal of organic heteroatoms (sulfur, nitrogen, oxygen, and metals) and partial, or full, saturation of aromatic hydrocarbons from various refinery streams. As the quality of crude oils decrease and the production of fuels and chemicals from alternative feedstocks (i.e., biomass, coal, oil shales, tar sands, etc.) increases, the hydroprocessing demand within the refinery will have to increase to meet the increasingly stringent environmental regulations placed on fuel specifications and the growing world-wide demand for diesel fuels. Furthermore as more alternative oils and heavy and extra-heavy oils enter the market, not only would hydrotreating demands increase for removal of heteroatoms and aromatics, but hydrocracking capacity can be expected to grow to increase production of gasoline, jet, and diesel fuels from heavier hydrocarbon fractions, such as vacuum gas oils (VGO), petroleum resid (bp>550° C.), and bitumen. Accordingly, a need exists for low pressure hydroprocessing methods and systems.